Graphic demand meter



April 15, 1941; G. w. ROSENBERGER GRAPHIC DEMAND METER Filed Sept. 50,1958 Emwb kg a m INVENTOR WlTNESSES:

Rosanayen ATTm ii W e W Patented Apr. 15, 1941 GRAPHIC DEMAND METERGeorge W. Rosenberger, Bloomfield, N. 1., assignor to WestinghouseElectric & Manufacturlng Company, East Pittsburgh, Pa., a corporation ofPennsylvania Application September 30, 1938, Serial No. 232,62. 6Claims. (Cl. 171-34) This invention relates to electrical instrumentsand it has particular relation to electrical instruments of the graphicdemand meter type.

In many instruments, an indicating member, such as a pointer or pen,travels or oscillates between fixed limits while the instrument, whichdrives the indicating member, operates con-' tinuously in one direction.An example of such an instrument is a graphic demand meter in which aninstrument movement, which may be of the watthour meter induction type,is employed for driving a register which integrates the watthourconsumption of an electrical load, and at the same time the movementactuates a pen for indicating on a chart a maximum demand for electricalenergy during successive intervals, usually of 15 or 30 minutesduration.

In operation, the pen is moved from a zero position to a positioncorresponding to the watthour consumption for the demand period. At theend of the demand period, the pen is returned to its zero position andthe chart upon which it leaves a record is advanced to receive a recordfor the succeeding demand interval. It occasionally happens that therelease mechanism for restoring the pen to its zero position fails tooperate. Under these conditions the pen would be actuated by theinstrument movement past its maximum recording position until it cameinto contact with some obstructing part of the instrument. When thisoccurs, the pen would impose an excessive load on the instrumentmovement with a resulting increase in wear thereon, and possibly with aresultant failure of the instrument to properly integrate the watthourconsumption on its integrating register. A similar condition mightobtain when the demand for any demand interval is in excess of that forwhich the instrument is designed, with a resultant movement of the penbeyond its maximum recording position. Although such occurrences arerare, instruments of this character are intended to remain in operationwithout attention for extremely long periods, and for that reason it isdesirable to include in the instrument a device for relieving theinstrument movement of this unusual burden.

Although a friction clutch may be included in the drive for the pen arm,which is designed to slip when the pen arm engages some obstruction asoutlined in the preceding paragraph, such a clutch is not entirelysatisfactory. Since it must be designed to transmit power to the pensuflicient for positively moving it from its zero to its maximumrecording positions, a clutch would have an undesirably high drag on theinstrument movement when the pen arm encountered an obstruction, and thereliability of operation of the clutch is, of course, affected by dustand climatic conditions.

-In accordance with my invention, the strain on the instrument movementis prevented when the pen arm meets an obstruction by separating a pairof gears used for transmitting power from interval for permitting thereturn of the pen to its zero position. I have found that such aconstruction requires few additional parts and imposes an unusually lowdrag on the instrument movement when the pen arm moves past its maximumposition suificiently to cause a separation of the gears.

It is, therefore, an object of my invention to decrease the drag on aninstrument movement when a member moved thereby passes a predeterminedposition.

It is a further object of my invention to separate a pair of gearsconnecting a pen arm to an instrument movement when the pen arm passesbeyond a predetermined position.

It is another object of my invention to provide a pair of gears betweenan indicating member and an instrument movement which are released atperiodic intervals to free the indicating member, and which are releasedwhen the indicating member moves, beyond a predetermined position.

Other objects of my invention will be apparent from *the followingdescription taken in conjunction with the accompanying drawing, in whichthe single figure represents a view in perspective, with parts brokenaway and parts removed, of a measuring instrument embodying myinvention.

Referring to the drawing, the single figure shows a graphic demand meterwherein an instrument movement, represented by a disc or armature i of awatthour meter movement, is employed for driving an integrating register2 through a plurality of gears 3, 4, 5 and 6. As is customary ininduction watthour meters, the

register 2 provides the watthour consumption of I 8. This pen arm ismoved in accordance with rotation of the disc I by means of a gear 9which meshes with the gear 4. The gear 9, in turn, through a shaft I0, aworm II, and a worm wheel I2, rotates a shaft I3 which drives a shaft I4carrying the pen arm I through a gear train I5. Preferably, the pen armI is hingedly mounted on a bracket I6 which is pivotally mounted on theshaft I4. Adjustment of the bracket I6 with reference to the shaft I4is'effected by rotation of a worm I? carried by the bracket, whichcooperates with a-worm wheel I9 mounted on the shaft I4. Acounter-balancing Weight I9 for the pen arm also is mounted on the shaftI4, and the pen arm is biased toward its zero'position by means of anadjustable weight 20 or any other suitable means.

The pen arm is driven across the face of the chart 8 during a demandinterval to leave a mark 2| which corresponds in length to the watt-hourconsumption during the demand interval. At the end of the demandinterval, the pen arm I is returned to its zero position, and the chart8 is moved upwardly for a short distance in preparation for a succeedingmovement 7 of the penarm 1. The return of the pen arm to its zeroposition is effected by separating the worm II and worm wheel I2 at theend of each demand interval. This separation is made possible bymounting one end of the shaft I3 in a rotatable bearing 22, which ismounted on a shaft The rotatable bearing 22 carries a stop lug 24, whichmay be moved into engagement with an adjustable stop 25. A stop 26limits outward travel of the stop lug.

Rotation of the bearing 22 for separating the worm II and worm wheel I2is effected through the shaft 23 by means of an arm 21, which has aprojection 28 for slidably receiving an operating rod 29. Movement ofthe operating rod 29 with reference to the arm 21 is restricted by apair of pins or stakes 39, 3I inserted in the rod 29 and by acompression spring 32, which is confined between the pin 3| and theprojection 28. The operating arm 29 may pass through a fixed guide 33for maintaining it in proper alignment.

The worm I I and worm wheel I2 normally are maintained in mesh by meansof a coil spring 34 which extends between a pin 35 fixed to the arm 21and a stationary pin or support 36. Because of the spring 34 actingthrough the arm 21 and shaft 23. the rotatable bearingnormally ispositioned against the adjustable stop 25 in which position the worm I Iand worm wheel I2 are held in mesh. When the operating rod 29 isactuated to the right as viewed in the drawing, it operates through thecushioning spring 32 to rotate the arm 21, shaft 23, and bearing 22 in acounter-clockwise direction such that the lug 24 is carried toward thefixed stop 26 in which position the worm II and worm wheel I2 areseparated.

In order to operate the rod 29 automatically at the end of each demandinterval, a timing cam 31 is provided for actuating and releasing theoperating arm 29 at appropriate intervals. In the specific exampleillustrated, the cam 31 operates through a cam follower 38, a bell crank39, and an actuating rod 40 to engage-a nut 4I adjustably threaded onthe end of the operating arm 29. The timing cam 31 may be rotated by anysuitable clockwork mechanism to raise and lower the cam follower 38 atthe end of each demand interval which, as before stated, ordinarily iseither of or 30 minutes duration. Consequently, when the mechanism thusfar described is in operation, the worm II and worm wheel I2 will bemomentarily separated and reengaged at the end of each demand interval.The period of separation of the worm II and worm wheel I2 is suflicientto permit the arm I under the influence of its biasing weight 20 to movefrom any position towhich it has been displaced to'its zero position. Inorder to stop the arm I in its zero position, a stop pin 42 is insertedin one face of the gear I2 for engagement with a movable stop segment43. This segment is provided with gear teeth which mesh with the teethof a worm 44 carried by the shaft I3, and is pivotally mounted on a fork45 carried by the shaft 23. As the pen arm I is advanced from its zeroposition, the stop segment 43 is advanced by the worm 44 out of the pathof the stop pin 42, thus permitting the gear I2 to make as manyrevolutions as required to move the pen arm I to its final position.When the worm and worm wheel are separated to free the pen arm I, thepen arm, in falling back to its zero position, rotates the shaft I3 andworm 44 to return the stop segment 43 into the path of the stop pin 42.

As heretofore explained, the structure thus far described provides anacceptable record of both the watthour consumption for a billing periodand the maximum demand occurring for the billing periods. However, ifthe timing cam 31 for some reason fails to separate the worm I I andworm wheel I2, or if an unusually heavy demand occurs during some demandinterval, the pen arm I will be carried beyond its maximum recordingposition depicted in dotted lines in the figure, until it may engagesome fixed part of the instrument. When this occurs, the resistanceoffered by the fixed part to further movement of the arm I imposes anexceptionally high load on the instrument movement which may wearexcessively or which may fail to operate the integrating register 2properly because of this excessive load.

' In order to relieve the instrument movement under these circumstances,a lever 46 ispivotally mounted on a bracket 41 attached to the frame ofthe instrument or register assembly. One end of lever 46 is slotted toreceive an extension of the pin 35 and the other end of the lever 46 ispositioned in the path of an arm 48 attached to the shaft I4 andcarrying an adjustable screw 49 for engaging the lever 46. When the penarm 1 is carried beyond a predetermined position such as that indicatedin dotted lines in the figure, the screw 49 engages the lever 46 androtates the lever in a clockwise direction as shown in the figure. Inthis rotation, the lever 46 through the pin 35 moves the arm 21, shaft23, and bearing 22 to separate the worm II and worm wheel I2 fromdriving engagement, thereby relieving the instrument movement from anexcessive load resulting from the engagement of a fixed part of theinstrument with the pen arm I.

The separation of the worm II and worm wheel I2 as a result'of theactuation by the screw 49 is not sufiicient in time duration to permitthe pen arm 1 to fall back to its zero position. As a matter of fact,the operation may be so adjusted that the tips of the teeth of the wormII and worm wheel I2 remain in engagement momentarily and merely slip byeach other as the disc I continues to rotate. Although this engagementis so slight that the resistance offered thereby to rotation of the discI is negligible, it is sumcient to prevent the return of the pen I toits zero position. Consequently, the pen arm I will remain in itsadvanced position until the timing cam 31 operates to release the penarm or until the meter reader notes that the meter is operatingimproperly.

It is believed that the operation of the mechanism described above isapparent. Recapitulating the operation briefly, rotation of the disc icontinuously advances the integrating register 2 in accordance with theload being measured by the instrument. Rotation of the disc I alsocarries the pen arm 1 across the chart 8 for a distance in each demandinterval corresponding to the load demand for the interval. At the endof each interval, the timing cam 31, through its connecting mechanism,rotates the bearing 22 to separate the worm H and worm wheel (2, therebypermitting the pen arm 1, under the influence of its biasing weight 20,to return to its zero position as determined by the stop pin 42 whichengages the stop segment 43 in the zero position of the pen arm. If thepen arm 1 should be carried beyond a predetermined position, such asthat indicated in dotted lines, the adjustable screw 49 through thelever 45 and associated mechanism rotates the bearing 22 sufficiently toreduce the load on the disc I without necessarily permitting the pen armI to fall back to its zero position. The return of the pen arm underthese circumstances is effected by proper operation of the timing cam 31or by the meter reader who, at'the end of the billing period, noticesthe advanced position of the pen arm.

Referring to the operation of the apparatus illustratedin the drawing ingreater detail, it should be noted that the timing cam 31 rotatescontinuously in the direction of the arrow at a uniform rate. At the endof each demand interval which, as above indicated, may be of minutesduration, one of the protuberances on the timing cam momentarily engagesand lifts the cam follower 38. This, in turn, rotates the bell crank 39in a clockwise direction and the bell crank forces the actuating rod 40to the right, as indicated by the arrow, into engagement with the nut 4|on the operating arm 29. Under the influence of this actuation, theoperating arm 29 moves to the right, as indicated by the arrow, andcarries with it the arm 21.

The movement of the arm 21 operates to rotate the shaft 23 in acounterclockwise direction, as indicated by the arrow surrounding theshaft. In rotating, the shaft 23 carries with it the bearing 22 intoengagement with the stop 26. Since the shaft I3 is supported at one endby the hearing 22, the movement of the bearing operates to separate theworm I l and worm wheel l2. The shaft i3 consequently is free to rotatein response to the bias of the adjustable weight in order to permit thereturn of the pen arm 1 to its initial position, shown in full lines inthe drawing.

When the timing cam 31 has advanced sufliciently for a protuberance toclear the cam follower 38, the various parts return to the positionsindicated in the drawing, with the worm II and worm wheel l2 again inmesh. In this condition, the apparatus again is effective to advance thepen arm '1 to a position corresponding to the demand for a succeedingtime interval.

-If the pen arm 1 for any reason should be advanced beyond the positionshown in dotted lines, the adjustable screw 49 is carried intoengagemeat with the lever 46. This lever,;through the pin 35 tendstorotate the arm Hand the shaft 23 in a counterclockwise direction asindicated by .the arrow around the shaft. Such movement of the shaft 23rotates the bearing 22 towards the stop 26 and separates the gears H andI2.

When the separation movement of the worm l I and worm wheel I2 is justsuflicient to permit one of the teeth on the worm wheel l2 to slip pastthe teeth of the worm II, the pen arm 1 tends to fall back towards itsinitial position. However, as the pen arm starts to fall back towardsits initial position, the adjustable screw 49 is carried away from thelever 46 and this release of the lever 46 permits the worm and wormwheel to return into full engagement. As a matter of fact, a slightoscillation-of the pen arm is produced by the slippage of the worm andworm wheel II and i2, butthis is so imperceptible that it could hardlybe noticed-by the naked eye. Consequently, when the pen arm I isadvanced beyond the position shown in dotted lines, the

teeth on the worm ll tend to ride over the teeth on the worm wheel l2without advancing further the pen arm. Because of the prompt return ofthe worm and worm wheel into full engagement when the screw 49 leavesthe lever 45, the pen arm I is held substantially in the position shownin dotted lines. This slippage of the teeth on the worm and worm wheelis accompanied by so little friction that the drag imposed thereby onthe meter disc I is not objectionable.

Although I have described my invention with reference to a specificembodiment thereof, it is obvious that numerous modifications thereofare possible. Therefore, I do not wish my invention to be restrictedexcept as required by the appended claims when interpreted in view ofthe prior art.

' I claim as my invention:

1. In an instrument, movable indicating means, means for moving saidindicating means in accordance with a variable quantity to be measuredincluding a coupling device, means cooperating with said coupling devicefor restoring said indicating means to a predetermined condition atpredetermined time intervals, and means effective if said indicatingmeans passes its intended maximum indicating position for rendering saidcoupling device ineffective.

2. In an instrument, a movable element, means for actuating said elementin accordance with a variable quantity to be measured including acoupling device, means for momentarily releasing said coupling device atpredetermined time intervals, and means for releasing said couplingdevice if said movable element reaches a predetermined position.

3. In an instrument, movable indicating means biased towards a firstposition, means for moving said indicating means against said bias inaccordance with a variable quantity to be measured including a pair ofgears normally biased in meshing engagement, means for restoring saidindicating means to a predetermined condition at predetermined timeintervals, and means responsive to movement of said indicating means toa predetermined position for rendering said meshing engagementineffective for advancing said indicating means. 1

4. In an instrument, movable indicating means biased towards a firstposition, means for moving said indicating means against said biasineluding a coupling device, and means efiective when said indicatingmeans is moved to a predetermined position for decreasing said couplingto a value insuflicient for advancing said indieating means against saidbias, but sufllcient for retaining said indicating means substantiallyin said predetermined position.

5. In a demand instrument, a-maximum demand indicator, a first gear,means for rotating said gear in accordance with a quantity to bemeasured, a shaft, a pair of spaced bearings for said shaft, one or saidbearings being mounted for rotation about an axis spaced from saidshaft, a second gear mounted on said shaft, said gears being normallybiased in driving engagement, and means for rotating said rotatablebearing for demeshing said gears including a first actuating device forperiodically oscillating said rotatable bearing and a second actuatingdevice for rotating said rotatable bearing in response to movement ofsaid indicator past a predetermined position.

6. In a maximum demand measuring instrument, means movable to a positionduring each of a plurality of predetermined time intervals correspondingto the demand for each of said intervals, actuating means for movingsaid movable means in accordance with a variable quantity to be measuredto said position for each of said time intervals and for releasing saidmovable means at the end of each or said time intervals, and meansresponsive to the position of said movable means for preventing afurther movement of said movable means by said actuatin: means.

GEORGE W. ROSENBERGER.

